The present invention relates to a protective inflatable bag assembly mounted on a vehicle for restraining an occupant in the event of a collision while the occupant is seated and, more particularly, to an inflatable bag assembly advantageously constructed and arranged to inflate a bag in a curved configuration.
An inflatable bag assembly is a typical protective implementation for restraining a vehicle occupant from moving forward due to inertia in the event of a collision, thereby preventing the occupant from hitting against a steering wheel or an instrument panel. Specifically, an inflatable bag assembly has a gas generator for emitting a gas in the event of a collision, and a bag to be inflated by the gas. As the gas generator is ignited, the bag is inflated in a moment toward a vehicle occupant to receive the occupant who tends to move forward. The bag is usually accommodated in a folded position in a retainer case which is mounted on a steering wheel or an instrument panel which is located in front of the occupant. The gas generator has a gas outlet which faces the inner periphery of the bag.
It has been customary to arrange the bag substantially evenly in the retainer case and to locate the gas outlet of the gas generator at the center of the retainer case.
To allow the inflatable bag assembly to effectively receive an occupant, it is preferable that the bag in the inflated position contacts the front of the occupant over a broad area. A prerequisite is, therefore, that the bag be provided with a flat shape at the final stage of inflation.
However, when the gas outlet is located to face the central portion of the bag as stated above, the bag begins to inflate at a central portion thereof in the event when the assembly is operated. Assuming the bag is configured to have a flat configuration at the final stage of inflation, the central portion of the bag entrains a peripheral portion in the direction of gas emission at the initial stage until the peripheral portion has been fully stretched. After the central portion of the bag has been bulged to a considerable degree, the peripheral portion bulges sideways due to the increase in the pressure in the bag while the central portion, in turn, recedes. Consequently, the bag reaches the predetermined configuration. In this manner, the bag flutters during the course of inflation and is apt to fail to reach the desired configuration at an adequate timing.
To eliminate the above problem, bulging of the central portion of the bag may be restricted by cords or similar implements, as disclosed in Japanese Patent Publication No. 43890/1981 and corresponding U.S. Pat. No. 3,074,693. This kind of implementation, however, increases the production cost of such a protective bag assembly because a number of cords have to be arranged in the bag and each has to be affixed at opposite ends thereof to the central portion of the bag and the retainer case.
To promote effective restraint on the occupant, it is often desired that the bag be inflated in an irregular configuration. Concerning the assembly assigned to the driver's seat, for example, the retainer case is disposed at the center of a steering wheel which faces the occupant of the driver's seat so that the bag may bulge out from the retainer case to receive the upper part of the occupant. In this instance, it is desirable to restrain not only the upper part but also the abdomen of the occupant by inflating the bag in the downward direction also. On the other hand, an instrument panel that faces a seat next to the driver's seat, i.e., assistant driver's seat has a ventilation duct or the like in its rear upper end portion as viewed in the front-and-rear direction of the vehicle. This portion, therefore, does not have a space large enough to accommodate a protective bag assembly. Hence, the assembly associated with the assistant driver's seat has to be mounted on the upper end of the instrument panel that is located in front of the seat of interest. In order that such a bag which bulges out from the retainer case may restrain the occupant of the assistant driver's seat, it has to be extended as far as the position between the rear end of the instrument panel and the occupant, i.e., it has to be curved by a large angle rearward and downward. Even if cords are used as stated earlier, it is difficult to regulate the configuration of such a bag which is to be curved by a large angle as stated above.